We propose to investigate the nutrient pathways of monkey, chicken, rabbit, and canine flexor tendons and tendon grafts within the synovial sheath, as well as the nutrition of extensor tendons of monkeys where they are surrounded by synovium. The uptake of radioactive tritiated proline by defined tendon segments, using various tendon preparations, will be investigated. We also propose to use autoradiography to determine the pattern of distribution of radioactivity within the substance of the tendon. We also propose to study in vitro healing of rabbit and chicken flexor tendons in various organ culture media.